This invention relates to a continuous vaporphase process for the manufacture of dialkyl sulfides by reacting alkanols and hydrogen sulfide in the presence of zeolite catalysts. More particularly, it relates to a process for the continuous manufacture of dimethyl sulfide (DMS) from methanol and hydrogen sulfide in the presence of a solid zeolite catalyst having a reduced alkali metal content.
DMS is a well known article of commerce, being used as a gas odorant, as a sulfiding agent for the post-regeneration treatment of hydrodesulfurization catalysts in petroleum refining, and as an intermediate for the manufacture of the specialty solvent dimethyl sulfoxide. In the past, the commercial requirements for DMS have been largely met by extraction from "black liquor" in wood pulp and paper operations and as a by-product from the manufacture of methyl mercaptan. Recently, however, the markets for DMS have outstripped its availability from these conventional sources, and there is now a need to manufacture additional quantities by independent means. The process of this invention provides an efficient method for producing DMS commercially.
It has been known for some time that DMS is produced as a by-product when methanol and hydrogen sulfide are reacted over dehydrating catalysts such as thoria, zirconia, and alumina to make methyl mercaptan. [E. E. Reid, Organic Chemistry of Bivalent Sulfur, Volume 1, p. 38 (1958), Chemical Publishing Co., Inc., New York]. Past research efforts in this area have centered on the development of more selective catalysts to favor the formation of methyl mercaptan over dimethyl sulfate, since supplies of the latter as a by-product from methyl mercaptan manufacture and pulp and paper operations exceeded its market demand. Examples of such mercaptan-selective catalysts are alumina promoted with alkali metal tungstates (U.S. Pat. No. 2,786,079 and U.S. Pat. No. 2,820,062) and with heteropolyacids and their alkali metal salts (U.S. Pat. No. 3,035,097).